1. Field of the Invention
The present invention relates to a variable displacement compressor suitable for use in an automobile air conditioning system, for example, and so constructed as to compress a refrigeration medium or the like working fluid and adjustably displace the thus compressed refrigeration medium.
2. Description of the Related Art
A typical example of variable displacement compressors of the type described is disclosed in Japanese Patent Laid-open Publication No. 62-157291. The disclosed variable displacement compressor includes a cylinder and a rotor rotatably received in the cylinder and carrying thereon a plurality of radially movable sliding vanes. Front and rear side blocks are disposed at opposite ends of the cylinder so as to define between the cylinder, rotor, vanes and side blocks a plurality of compression chambers. The front side block is provided with a displacement adjustment mechanism for controlling the amount of refrigeration medium to be withdrawn for compression from intake holes into the compression chambers, thereby adjusting the displacement of the compressor according to various operating conditions of the compressor.
The displacement adjustment mechanism may be provided on the rear side of the compressor in which instance the front side block is formed with a lubrication oil passageway for lubrication of the displacement adjustment mechanism. The lubrication oil passageway opens at its opposite ends to a high pressure oil sump and to an end face of the rotor. In operation, the lubrication oil is fed to flow out from a clearance between the front side block and the rotor, then lubricates a bearing supporting a shaft, and flows through a longitudinal central groove in the shaft to the rear side of the cylinder. Thereafter, the lubrication oil flows into a bearing and the displacement adjustment mechanism for lubricating the same.
With this construction, the lubrication oil is subjected to a succession of choking actions or flow resistances as it flows through a long flow path to the displacement adjustment mechanism, and hence a sufficient supply of lubrication oil is difficult to obtain. This insufficient lubrication oil supply is likely to cause seizing of sliding surfaces of moving parts due to the shortage of lubrication oil.